Another method is this. Add kiss to the YouTube url. For example, the url is http://www.youtube.com/watch?v=tRTk0RPXtW4, so you just add kiss before youtube and it becomes http://www.kissyoutube.com/watch?v=tRTk0RPXtW4! Unfortunately the Online download is down until further notice.

Update: Another one for you. You can try download youtube videos using KeepVid